Breeding biology and nest survival of the Rusty-backed Antwren (Formicivora rufa)

Abstract

Breeding biology data are crucial for avian life history theory, but this information is unavailable for nearly half of the current living tropical bird species. Predation is the main driver of nest survival among tropical birds, and spatial and temporal factors may affect nest predation risk and survival. In this study, we describe the breeding biology of the Rusty-backed Antwren (Formicivora rufa), a bird that inhabits a coastal sandy plain in southeastern Brazil, and examine the effects of date and microhabitat features on nest survival. We found 47 nests over 2 breeding seasons. The nesting season lasted 7–8 months. The mean (± SD) nest-building time was 7.3 ± 1.1 d, the mean incubation period was 16 ± 1.9 d, and nestlings remained in the nest for 10 ± 0.8 d for a full nesting cycle that lasted for ∼26 d. Clutches invariably had 2 eggs and egg-laying occurred over 2 consecutive days. Males and females were both observed building nests, incubating eggs, and feeding nestlings and fledglings. We also report a nestling with a depigmented body, which may represent albinism. Most nests were depredated (68.1%, n = 32). Nest survival was constant throughout the breeding seasons and did not vary with microhabitat features (nest height above the ground, and vertical and horizontal distances between nest and shrub edges). The nesting biology of the Rusty-backed Antwren fits the general pattern typical of antbirds, and micro-spatial or temporal features cannot predict nest survival in our study population.